A disc-type recording medium (in the following, called an “optical disc”), to which optical reading is applied, such as a DVD (Digital Versatile Disk), a CD (Compact Disk), etc., has rapidly become widespread for use in storing computer files and moving-image streams. An optical disc has a large storage capacity and is capable of random accessing. Also, unlike a contact-type magnetic recording medium, there is no concern for abrasion and damage on the recording face by reading, head crash, etc. Also, the disc surface is strong, and there is low risk of accidental data loss. In recent years, recording/playback apparatuses using optical discs, such as a DVD-R, a DVD+R, and a CD-R have also been developed and manufactured, and the optical discs are widely used, for example, for external recording media and external storage devices for computers.
For example, the UDF (Universal Disk Format)(a registered trademark) defined by OSTA (Optical Storage Technology Association) is known as an optical disc format having high compatibility (For example, refer to Non-patent document 1). The UDF corresponds to an implementation technique of the ISO/IEC 13346 standard (the ISO/IEC 13346 is a successor of ISO9660, and is corresponding to increases in disc capacity and the number of files), which is known as ECMA (European Computer Manufacturer Association) -167 (For example, refer to Non-patent Document 2). In 1990s, the UDF has become wide spread for use as a writable optical disc together with price reduction of CR-RW media and CD recording apparatuses.
In the UDF, by adopting a packet-writing method, it is possible to perform processing, such as addition or deletion of a file to an optical disc through a normal file system. In the packet-writing method mentioned here, data is written with a packet structure in which a link block and four Run-In areas are provided before user data, and two Run-Out areas are provided at the end of the user data. The seven blocks are used as link areas (Linking Area), which are junction areas between adjacent packets except for the user data area. It is possible to write into the UDF from almost all the Operating Systems (OS), also the written files are file systems whose playback compatibility is achieved on the OSs without any special read programs, and the contents in an optical disc can be operated in the same method as a hard disk, a floppy disk, a USB (Universal Serial Bus) flash memory. However, in the cases of a recordable recording medium, such as a DVD-R, a DVD+R, and a CD-R, etc., deleted files are erased only from a directory, and are left as they are in the recording medium.
In the case of a recordable disc, such as a DVD-R, a CD-R, etc., there are restrictions that writing in a physical sector can be carried out only once, and data must be written continuously (incrementaly) toward the outer circumference without placing free logical sectors. This means that in the original UDF format, after data is pre-mastered, all the data must be written in one piece into a medium (similarly to the way of writing into CD media by ISO9660).
Thus, in order to allow files on a CD-R and a DVD-R to be modified virtually in the same manner as a hard disk, OSTA added a Virtual Allocation Table (in the following, called a “VAT”) and a method of recording using Virtual Partition Map to the UDF standard. The VAT is an additional data structure, on a disc, including a table for managing logical addresses at which files are actually recorded and virtual addresses corresponding to the logical addresses. When a file on a disc, or the other data is changed, a logical address can be relocated using the VAT, and thus it is possible to handle a medium to be written sequentially as if it is a medium allowing random reading and writing.
Accordingly, by attaching a VAT to a disc recording apparatus, it becomes possible for an only-once recordable recording medium, such as a DVD-R, a DVD+R, and a CD-R to record additionally.
The position of a VAT can be placed freely in a packet structure, but a VAT ICB (Information Control Block) pointing a VAT is determined to be placed at a sector backward as much as a link area from the final sector of the recorded area. For example, a proposal has been made of a data recording and playback apparatus (for example, refer to Patent Document 1) in which at data playback time, past recording data left on a recording medium can be referenced by reading a VAT other than the VAT recorded at the final end of the recorded area of the recording medium, and at data recording time, the VAT recorded on a recording medium is read in order to additionally record next to the final end of the recorded area of the recording medium. By this apparatus, at playback time, past record data left on the recording medium can be referenced by reading a VAT other than the VAT recorded at the final end of the recorded area, and at recording time, it is possible to restore a past recording state.
Here, in consideration of the convenience of a user, it is preferable that a recording medium additionally recorded in compliance with the UDF can be played back by a playback-only apparatus before being subjected to special processing, such as finalization, etc., that is to say, in a state of allowing additional recording. For example, still images, moving images, etc., captured by a digital camera and recorded on a DVD are taken out, loaded into a DVD player for outputting and displaying the images, and then loaded again into the digital camera to capture images.
However, many of disc-playback-only apparatuses which have already become widespread now, do not include VATs, and thus it is not possible for the disc recording apparatuses to maintain the compatibility with these existing disc-playback-only apparatuses. For example, there are reports from users that a moving-image DVD produced by a personal computer failed to be played back by set-top DVD players. The cause depends on whether the UDF to which each apparatus complies supports VAT or not. It is thought that disc-playback-only apparatuses to be on the market in the future is provided with VAT, but there is a problem in that the cost of the apparatuses will increase.
Patent Document 1
Japanese Unexamined Patent Application Publication No. 2001-351336
Non-Patent Document 1
http://www.osta.org/specs/index.htm
Non-Patent Document 2
http://www.ecma-international.org/publications/standards/Ecma-167.htm